A 78-year-old woman has become the first reported indigenous dengue fever case in Tainan this year, health authorities in the southern city announced Tuesday.

The woman living in Tainan's South District sought medical treatment and underwent screening for dengue Sunday after feeling unwell that day and coming down with a fever. She was hospitalized the following day, said Chen Yi, head of the city government's dengue fever prevention and control center.

The woman was later confirmed to have dengue virus type 4 (DENV-4), Chen said.

The Tainan health authorities also determined the patient to be this year's first indigenous dengue fever case in the southern city, according to Chen.

In addition, as of Monday, 13 imported dengue fever infections had been reported in Tainan, according to statistics compiled by the Tainan City government's Department of Health.

The city government has taken preventive measures against dengue fever such as disinfection and cleaning vector-breeding sites.

Nationwide, five new indigenous dengue fever cases were confirmed over the past week as of Sept. 10, including three in Taichung, one in New Taipei and one in Tainan, the Centers for Disease Control (CDC) announced Tuesday.

As of Sept. 10, the number of dengue fever cases around Taiwan had hit 107 this year, according to CDC statistics.

This year, Taiwan faces dengue fever outbreaks of four different virus types compared with the past few years, when only one type was reported in the country, CDC Deputy Director-General Chuang Jen-hsiang said, adding that this could be attributed to more international visitors entering Taiwan, Taiwanese people traveling overseas in large numbers, and the hot and wet weather in the country.

Taichung has been affected by virus type DENV-1, while New Taipei has been hit by DENV-2, Kaohsiung DENV-3 and Tainan DENV-4, Chuang added.

The CDC reminded residents to take precautionary measures when traveling to dengue endemic countries, and to seek treatment as soon as possible when symptoms of dengue fever, including fever, headache, severe muscle and joint pain, eye socket pain and skin rash become apparent. (By Chen Wei-ting and Evelyn Kao)